Direct electrophysiological recordings from human brains are a rare opportunity afforded by the clinical needs of patients undergoing intracranial monitoring for epilepsy surgery. The primary focus of the PI's R01 is on using microelectrode array recordings of local field potentials, multi-unit and single neuron activity to investigate th spatial properties of spontaneous seizures in the human brain, and how they are reflected in standard EEG. The PI's colleagues, included as major and minor users in this proposal, pursue R01-funded research in basic cognitive neuroscience that exploits the opportunity for more direct brain investigation in surgical epilepsy patients within the framework of the PI's clinical program. This proposal thus aims to extend significantly existing investigations of both pathological and normal function that are otherwise restricted to animal models or non-invasive EEG - a rare and almost unprecedented opportunity. We request funding for a clinically approved, 256-channel integrated recording system, capable of recording from many types of electrodes at variable sampling rates up to 30 kHz/channel. This system will allow us to obtain high quality EEG recordings across a spectrum of frequencies and spatial scales, precisely timelocked to unit activity. The compilation of all these data types into a single, cohesive data set with software tools conveniently provided on the instrument as well as those shared by the investigators will simplify and enhance data sharing among the group. We anticipate that this system will enable many future electrophysiological investigations in humans that make use of the burgeoning advances in clinical sensor technology in a variety of clinical and investigative fields.